Method and apparatus for heat setting false twisted yarn



METHOD AND APPARATUS FOR HEAT SETTING FALSE TWISTED YARN Filed Aug. 10,1959 F. SCRAGG May 5, 1964 2 Sheets-Sheet l I NVENTOR. freJaflzc/k.Semis! his m y y 5, 1964 F. SCRAGG 3,131,528

METHOD AND APPARATUS FOR HEAT SETTING FALSE TWISTED YARN Filed Aug. 10,1959 2 Sheets-Sheet 2 INVENTOR. fre/Jzrick scn gg' nnc/mz s. Sin/ml hisil'lii ornay United States Patent M t 3,131,528 METHOD AND APPARATUS FURHEAT SETTING FALSE TWISTED YARN Frederick Scragg, Tytherington, England,assignor, by mesne assignments, to Dcvokins Limited, Manchester, EnglandFiled Aug. 10, 1959, Ser. No. 832,659 Claims priority, application GreatBritain Aug. 16, 1958 Claims. (Cl. 57-34) The invention is concernedwith the provision of a new process for imparting certain desirablecharacteristics to textile yarns, and has for its object the provisionof means and apparatus for making a textile yarn from monofilaments andhaving mechanical and thermal properties resembling those possessed byyarns made from natural fibres.

Such natural fibre yarns are known to have a high degree of randomicityin the form of the individual fibres comprising the yarn. This arises inthe process of natural growth which always tends to produce similarstructures with slight differences rather than structures exactlyresembling one another. Yarn made from natural fibre therefore consistsof a series of approximately parallel twisted fibres, the twistingimparting strength to the yarn whilst the random kinks present onteachyarn cause the yarn to bulk uniformly along its length providing thatthe drafting processes preceding the spinning have been eficientlyperformed. This quality of uniformity combined with bulking, hashitherto been found difiicult to copy by yarns made from artificialfibres, since from their manner of production, such fibres are normallyof substantially uniform cross-section, straight and smooth, andhaveuniform physical properties throughout their length. Again,manufacturing processes lend themselves more readily to the productionof continuous monofilaments than to staple fibres of random length. As aresult, yarns made directly from a bundle of monofilaments to which arelatively low rate of twist has been imparted, tend to be inelastic,non-bulking, smooth and cold to the touch.

Various attempts have been made to overcome these disadvantages and toproduce monofilament yarns, more particularly a yarn constructed fromthermoplastic monofilarnents, which tends to bulk or fluff, and aconsiderable measure of success in this direction has been achieved.Certain disadvantages however are still remanent in such bulk yarns. Forexample, if a yarn is made by imparting a high degree of twist to it,setting the twist in the yarn and then untwisting it, the resulting yarntends to be too bulky, and has too high a degree of natural contraction.In addition, a certain amount of residual torque may remain in the yarn,which if no measures are taken to prevent it, causes garments made fromthis yarn to distort in a spiral manner. Again, in another type of bulkyarn, the process tends to cause uneven dyeing although there is noremanent torque.

The invention provides a partially bulked yarn in which the previouslyrecited disadvantages are wholly or mainly overcome by the treatment towhich the yarn is subjected. The process is applicable to thermoplasticyarns, i.e., those composed of filaments of which the material softensprogressively as its temperature is raised, any distortion or formapplied to the filaments whilst so heated being retained whenthefilaments are cooled. The object of the invention may therefore berestated as being the production of a moderately bulked yarn constructedfrom a plurality of thermoplastic monofilaments, the said yarnexhibiting little or no residual torque and having a small or zerocontraction in length when freely suspended in air.

To produce this yarn, I may adapt a machine similar to that of thenormal uptwister employed in connection 3,131,528 Patented May 5, 1964withmonofilament yarns. I provide a yarn package and support preferablyat the base of the machine, and a pair of feed rollers above it, theyarn passing through the nip of the rollers and being drawn off at apredetermined rate. The yarn may receive a relatively low degree oftwistsay two to four turns per inchbefore being wound onto the package,or alternatively it may be ringtwisted as it is being drawn from thepackage. From the feed rollers the yarn passes over a suitable heaterwhich may be in the form of a convexly curved plate, the temperature ofwhich is set to and controlled at a temperature found by experience tobe suitable for treating the yarn concerned. Thereafter the yarn passesthrough a cooling zone which may be merely a predetermined distance ofpassage through air at ambient temperature and then through a falsetwist sprindle which imparts a high degree of twist to the yarn. Thistwist runs backwards to the heated face of the plate where it is set inthe yarn, causing the filaments of the latter each to assume asubstantially spiral formation, this twist being fixed during itspassage through the air space.

. When leaving the false twist device, the formation of each filament ischanged from that of a spiral to a substantially straight or slightlycurved or undulating form, though in so doing it should be noted thatthe false twist device, although removing the spiral formation, insertstorque in each filament as a result of the unwinding of the spiralimparted to the filaments. The yarn is drawn away from the false twisterby a second pair of feed rollers, the peripheral speed of which ispreferably in the region of the peripheral speed of the input feedrollers located below the heating zone. If found desirable, the secondfeed rollers may draw the yarn at a slightly less rate than that of theinput feed rollers to allow for yarn contraction in the heating zone.The yarn is now wound on a package or cheese, the peripheral speed ofwhich is maintained constant at a value considerably lower than that ofthe second pair of feed rollers. Thus if the rate of delivery of theyarn from the second feed rollers is feet a minute, then the peripheralspeed at which the yarn is wound onto the cheese may be between 60 and70 feet a minute. The peripheral speed of the wind-up cheese may bemaintained constant by allowing the cheese to rest rotatably on thesurface of a driven roller, or by the use of a suitable infinitelyvariable gear acting on the spindle of the cheese.

Considering the physical characteristics of the yarn wound on thecheese, it will be found that each filament now has a series of randomor partially random kinks or small loops formed on it by the effect ofthe false twist device in unwrapping the spiral shape given to thefilaments and set by the heating zone. There is also a tendency on thepart of each filament to contract lengthwise, and in addition eachfilament exerts a torque which is the result of the untwisting providedby the false twist device after twist has been set in the heater. Onlythe first of these three characteristics is desirable, since this is theone which provides moderate bulk to the yarn. The tendency to contractwould cause the yarn to shorten excessively, or alternatively if theyarn were made into a garment, the garment would be smaller in an unwornthan in a worn condition. Finally, the inherent torque of each filamentwould cause the yarn composed from the filaments to tend to twist, andto impart twist to garments made from it. It is therefore now requiredto remove residual shrinkage and torque from the filaments.

To this end, I heat the yarn either on or before it reaches the cheese asecond time to a temperature at which intermolecular strains arereduced, i.e., the material is annealed. Since each filament has aslightly wavy or undulating shape, and since only a low tension isapplied to the filaments whilst they are wound, there is litthe heaterand Whilst it is subject to false twist.

tle or no tendency for this undulating form to be removed. There ishowever both a compulsion onthe yarn which prevents its additionalcontraction, and a compulsion which prevents the yarn frorn twisting,with the result that if heat of sufficientamount is applied for anappropriatetime to the yarn, both longitudinal and twist stresses in theyarn are greatly reduced or removed. As a result, the finished yarnpossesses an appreciable bulk, little extension under load, and very lowor zero tendency to twist. Since real twist was initially imparted tothe yarn and still remains therein, the bulking effect is limited, andadjacent yarns do not appreciably coalesce. Again, since the undulationsof each monofilament are restricted in amplitude, the material has ahandle similar to that of yarns made from natural fibres.

To effect the heating of the material on the cheese I provide an oven inthe form of a cover which encloses as much as possible of the cheeseitself. The oven has an inner radius of curvature which is somewhatgreater than that of the maximum radius achieved by the material duringwinding on the cheese, and the inner surface of the oven is providedwith one or more heater strips preferably with reflectors so as todirect the heat produced at the yarn, and reduce the amount of heat lossoutwards through the body of the oven, which is either of heatinsulating material, or which contains heat insulating material as afilling. The cover is supported in such a way' as to keep its innersurface as nearly as possible concentric with the surface of the cheeseas it is being Wound. Again, the oven is so supported that it can bereadily moved away from the cheese so that the latter can be removedafter winding.

Although the former method of heating the yarn after the false twistingstage enables the yarn to be kept hot during part or all of the windingtime, the method may present certain disadvantages and I therefore havedevised an alternative method of heating the yarn which consists Theyarn emerging from the top nip rollers 13 and 19 (FIG. 3) is collectedto form the package 8 shown in FIG. 1. The package 8 rests on the drivenroller 1 which has a constant speed of rotation less than the rate ofdelivery of the yarn from the rollers 18, 19. Thus, if the rate ofdelivery from the latter rollers is 100 feet a minute, then theperipheral speed of the package 8 'provided by the driven roller 1 maybe between 6 and 70 feet aminute. t 7

As is evident from FIG. 1 the package 8 is supported on an arm 2 whichis itself pivotally supported by a shaft 7 carried by a support 10.

To effect the heating of the package 8 an oven is provided, this oven 6(FIGS. 1 and 2) forming a cover in which the package 8 is located. Theinner radius of curvature of the oven 6 is somewhat greater than themaximum radius achieved by the yarn during winding onto the package 8,and the inner surface of the oven is provided with a plurality ofelectricalheating strips 4 as well as with reflectors which direct theheat to the yarn so as to reduce the amount of heat loss outwardsthrough the body of the oven. The material of the oven 6 may be heatinsulating, or as shown in FIG. 1 a layer of heat insulation 5 lines theinner surface of the oven, and the heater strips 4 are located at'theinner surface of the insulation layer 5.

The. partially cylindrical cover 6 is supported in such a way as to keepits inner surface as nearly as possible concentric with the surface ofthe package 8 as the lat- 1 that of the shaft 7, and thus as thediameter of the packin winding the yarn after it has left the top pairof feed rollers, on to the surfaces of a pair of rollers having aplurality of grooves, the. grooves being so arranged that yarn travelsfrom one end of the rollers to the other during its passage round them.One or both of the rollers is or are heated to a temperature sufiicientto cause the relaxation or removal of molecular strains in the yarn asit passes over the rollers. The. peripheral speed of the said rollers isappreciably less than that of the peripheral speed of the feed rollers,so that the yarn is in a partially bulked condition as. described aboveduring application of the heat treatment to it. After leaving the heatedrollers. the yarn is wound on a cheese the peripheral speed of which issubstantially the same as that of the rollers.

The yarn may or may not be further heated whilst wound' on the cheese,but it is thought that such further heat treatment may be unnecessary.

Reference should now he made to the accompanying drawings in which FIG.1 is a side view of the windup mechanishm and heating oven which wepropose to employ in connection with the final processing to be appliedto our yarn, FIG. 2 is a plan view of FIG. 1, and FIG. 3 is a side viewof a diagrammatic representation of one half of a machine for carryingout my process.

Referring to'FlG. 3, it Will be seen that a yarn package 12 is providedin the base of the machine, located on a support 11. Yarn is drawn fromthe package through a yarn stabiliser 14 by means of nip rollers 13 and15. Yarn is then pulled over the surface of a heater 16, the temperatureof which may be automatically stabilised, and through afalse twist tube.17 by means of further nip rollers 19 and 13. The peripheral speeds ofthe two roller assemblies are adjusted so that a small amount ofshrinkage takes place in the yarn whilst it passes over The yarn mayreceive a relatively low degree of twist-say two to four turns perinch-before being wound onto the package, or alternatively it may bering twisted as it is being drawn from the package.

age 8 increases the arm 2will turn in a clockwise direction around theshaft 7, as viewed in FIG. 1, thus causing the bell crank 9 to turn in acounterclockwise direction, as viewed in FIG. 1, and in this way theupper arm of the bell crank by engagement with the arm 3 will turn thelatter in a clockwise direction around the shaft 7, as viewed in FIG. 1,so that in this way the inner surface of the oven is maintained asubstantially constant distance from the exterior surface of the package8 during' winding thereof. As is apparent from FIG. 2 the oven 6 can bemanually turned at any time, independently of the arm 2, around theshaft 7 in a clockwise direction, as viewed in FIG. 1, so as to removethe oven from its position enclosing the package 8 to enable the latterto be removed from the arm 2. The yarn as it is taken from package 8 isonly contractile to a small degree, but remains fully bulked.

The arrangement of levers 2, 3 and 9 is so dimensioned that as thepackage grows in size, the spacing, between the heaters 4 and thesurface of the package remains substantially constant. When the package8 is fully wound, the heating oven is lifted away from it, pivotingabout the shaft 7. The package is removed from its arm 2 and is replacedby an empty support, and the process of crimping is renewed by loweringthe oven.

Although the former method of heating the yarn after the false twistingstage enabled the yarn to be kept hot during part or all of the windingtime, the method may present certain disadvantages and in an'alternativeembodiment of the invention the yarn after it has left the top pair ofnip rollers 18, 19 is fed onto the surfaces of a pair of spacer rollershaving a plurality of grooves, the grooves being so arranged in knownmanner-that yarn travels from one end of the rollers to the other duringits passage round them. ()ne or both of the rollers is heated to atemperature sufiicient to cause the relaxation or removal of molecularstrains in the yarn as it passes over the rollers. T he peripheral speedof the said rollers is considerably less than that of the peripheralspeed of the feed rollers 18, 19 so that the yarn is in a partiallybulked condition as described above during application of the heattreatment to it. After leaving the heated rollers the yarn is wound on acheese the peripheral speed of which is substantially the same as thatof the rollers. The yarn may or may not be further heated whilst woundon the cheese, but it is thought that such further heat treatment may beunnecessary.

Although the invention has been described in connection with the use ofnip rollers 13 and 15 for removing yarn from the supply package, itshould be understood that the said rollers may be omitted, the yarnbeing drawn through the machine by the top nip rollers 13 and 19. A yarntensioner or stabiliser located between the supply package and theheater then replaces the rollers 13 and 15.

What I claim is:

1. A method of producing a bulked yarn of thermoplastic textilemonofilaments in a continuous process consisting in continuouslywithdrawing the yarn from a suitable package, passing the yarn through aheating zone, passing the yarn through a false twist device so as toimpart twist to the yarn, drawing the yarn through the said twist deviceat a predetermined speed, Winding the yarn onto a further package at aspeed lower than that of the said predetermined speed, and subjectingthe yarn to a further heat treatment after it is wound on said furtherpackage, the time and temperature of the second heat treatment beingadjusted so as to remove at least some of the internal stresses of theyarn at said further package.

2. Yarn-treating apparatus comprising drawing means for drawing the yarnfrom a package and through the apparatus at a constant rate, a heateralong which the yarn passes, means for applying false twist to the yarnso that part of the twist runs backwards into the heater and is settherein in the yarn, a yarn package for collecting the yarn, means fordriving the said package so that its peripheral speed is less than saidconstant rate of the drawing means, and package-heating means forheating the yarn while it is wound on the package.

3. Apparatus according to claim 2 in which the package heating meansconsists of an oven which is arranged to cover the yarn package and toheat the yarn thereon during winding of the package.

4. Apparatus according to claim 2 in which the yarn drawing meanscomprise two pairs of nip rollers.

5. Apparatus according to claim 2 in which the yarn drawing means is apair of nip rollers located between the false twist means and the yarnreceiving package, the yarn passing through a stabiliser or tensioningdevice located between the yarn delivery package and the heater.

6. For use in an apparatus of the character described, a device forheating yarn while it is wound onto a package, comprising incombination, an elongated arm; support means supporting said armadjacent one end thereof for turning movement about a given axis;package supporting means carried by said arm adjacent an opposite endthereof for supporting a package during the winding thereof; drivenroller means located beneath said opposite end of said arm for engaginga package and rotating the same; a heating oven enclosing the space inwhich the package is located; and means cooperating with said oven andsaid arm for maintaining an inner surface of the oven at a substantiallyconstant distance from the package during the winding thereof.

7. For use in an apparatus of the character described, a device forheating yarn while it is wound onto a package, comprising, incombination, an elongated first arm; support means supporting said firstarm adjacent one end thereof for turning movement about a given axis;pack age supporting means carried by said first arm adjacent an oppositeend thereof for supporting a package during the winding thereof; drivenroller means located beneath said opposite end of said first arm forengaging a package and rotating the same; a heating oven enclosing thespace in which the package is located; a second arm fixed to andcarrying said oven and supported by said support means for turningmovement about said given axis; and bell crank lever means turnableabout an axis parallel to said given axis, and having a pair of armsrespectively engaging and located between said first and second arms,said bell crank lever means transmitting turning of said first arm tosaid second arm for maintaining said oven at a substantially constantdistance from the package during the winding thereof.

8. The combination of claim 6 and wherein a yarn treating means treatsthe yarn as it approaches said driven roller means so that any stressesin the yarn resulting from treatment thereof by said yarn treating meanswill be at least partly eliminated during heating of the yarn in saidoven.

9. The combination of claim 7 and wherein a yarn treating means treatsthe yarn as it approaches said driven roller means so that any stressesin the yarn resulting from treatment thereof by said yarn treating meanswill be at least partly eliminated during heating of the yarn in saidoven.

10. Yarn-treating apparatus comprising drawing means for drawing theyarn from a package and through the apparatus at a constant rate, aheater along which the yarn passes, means for applying false twist tothe yarn so that part of the twist runs backwards into the heater and isset therein in the yarn, a yarn package for collecting the yarn, meansfor driving said package so that its peripheral speed is less than saidconstant rate of the drawing means, and package-heating means forheating the yarn while it is wound on the package, the packageheatingmeans consisting of an oven which is arranged to cover the yarn packageand to heat the yarn thereon during winding of the package and in whicha means cooperates with the oven for maintaining an inner surfacethereof at a substantially constant distance from the package during thewinding thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,854,040 Junkers Apr. 12, 1932 2,306,401 Miles Dec. 29, 1942 2,421,334Kline et al May 27, 1947 2,639,485 Ambler May 26, I953 2,803,105Stoddard et a1 Aug. 20, 1957 2,823,513 Van Damme et al Feb. 18, 19583,029,591 Scragg et a1. Apr. 17, 1962 3,077,724 Stoddard et a1 Feb. 19,1963 FOREIGN PATENTS 787,619 Great Britain Dec. 11, 1957 531,481 ItalyAug. 2, 1955

10. YARN-TREATING APPARATUS COMPRISING DRAWING MEANS FOR DRAWING THEYARN FROM A PACKAGE AND THROUGH THE APPARATUS AT A CONSTANT RATE, AHEATER ALONG WHICH THE YARN PASSES, MEANS FOR APPLYING FALSE TWIST TOTHE YARN SO THAT PART OF THE TWIST RUNS BACKWARDS INTO THE HEATER AND ISSET THEREIN IN THE YARN, A YARN PACKAGE FOR COLLECTING THE YARN, MEANSFOR DRIVING SAID PACKAGE SO THAT ITS PERIPHERAL SPEED IS LESS THAN SAIDCONSTANT RATE OF THE DRAWING MEANS, AND PACKAGE-HEATING MEANS FORHEATING THE YARN WHILE IT IS WOUND ON THE PACKAGE, THE PACKAGEHEATINGMEANS CONSISTING OF AN OVEN WHICH IS ARRANGED TO COVER THE YARN PACKAGEAND TO HEAT THE YARN THEREON DURING WINDING OF THE PACKAGE AND IN WHICHA MEANS COOPERATES WITH THE OVEN FOR MAINTAINING AN INNER SURFACETHEREOF AT A SUBSTANTIALLY CONSTANT DISTANCE FROM THE PACKAGE DURING THEWINDING THEREOF.